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topic 8957

Q.P.Q. Process



A discussion started in 2000 & continuing through 2017

(2000)

Q. I'd like to now more about QPQ, or other similar nitriding / nitrocarburizing + black oxidation process.

Which kind of salt is used in the QPQ process. What kind of cleaning processes have to be used before nitriding and before oxidation. What environmental problems result from using this salt, in particular the quenching one? Is it possible to couple a gas nitriding process to a QPQ but only for the quenching-oxidising process?

Does there exist other similar HT with the same surface finishing (very important is uniformity and real black colour)? Thanks in a advance for any help.

L. Gessi
- Opera (MI) Italy


(2000)

A. Hi L.,
Kolene offers the QPQ process and has put a paper about it on-line on this site.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



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(2001)

Q. I have a specification for finishing a 303SS thumb screw which calls out (Melonite Q.P.Q.). Does anyone have any information on this process?

Michael Morrison
- Stafford, Texas, USA


(2001)

A. Hi Michael. The 'Q.P.Q.' part stands for Quench-Polish-Quench. Kolene has an article on line here about the Quench-Polish-Quench process at http:/www.finishing.com/kolene/qpq.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


(2001)

A. Hello Michael!

Melonite is an olde trademark of Lindberg Heat Treating for their salt bath nitriding, which they now call Lindure. The QPQ process is Kolene's name for their SBN variant (they quench-polish-quench to give better surface properties). So I don't think that there is a Melonite QPQ. (See below)

However, your best bet is to go right to the horses's mouth, at www.finishing.com/kolene/nitriding.html. Kolene lists a fair amount of info there. They also list a trade name index, at www.finishing.com/kolene/altern.html, which may prove interesting to you.

Good luck!

lee gearhart
Lee Gearhart
metallurgist



(2001)

A. MELONITE QPQ is a trademark of Houghton Durferrit GmbH, Germany. The MELONITE salt bath nitrocarburizing process is available at commercial heat treaters around the world.

Rainer Willing
- Valley Forge, Pennsylvania



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Advice on QPQ

(2002)

Q. We manufacture a conveyor belt scraper that consists of a mild steel shaft, a piece of mild steel channel, and two tensioners. We are looking into ways we can make the unit more corrosion resistant. Is QPQ a good option? Is it more cost effective than stainless? Should parts be prepared before coating? And, finally, does the coating replace paint?

Shaun Carnes
- Highland, New York


(2002)

A. I do not know what QPQ is.

On a practical side, for economic reasons, I personally would not recommend any coatings on a 'consumable surface'. Short of utilising abrasion resistant (and expensive)chromium or ceramic coatings or hard alloys I would recommend designing the scraper to take a quick-fitting sacrificial module on the workface (cheap). This would need to be a harder tool steel with a simple profile for cheap manufacture. Work life would be long and replacement time measured in minutes (Bolt on?). I would possibly recommend avoiding electrochemical corrosion by isolating the module from mild steel components with a nested block of polypropylene.

John Tuohy
- Ireland

Ed. note: We have an article on the Kolene QPQ process here at finishing.com/kolene/qpq.



Effect of QPQ on thread strength

(2004)

Q. I am a designer of hydraulic manifold blocks in the water hydraulic industry. These blocks have mounted valves, connection ports and cross drills on all surfaces. These manifolds are used in raw water and 95/5 systems with pressures up to 5000 psi. If carbon steel is used the material receives QPQ or gas nitriding treatment after machining. My question is do the threads lose any of their strength after either of these two corrosion resistant processes? Or do the threads increase in strength? I have not been able to find any information on this subject. Have any tests been done?

Chris Marconi
hydraulic design - St. Catharines, ON, Canada


(2004)

A. I don't know the answer to your question, but I would highly recommend you talk to Kolene about it. They are the experts on the QPQ process.

Toby Padfield
Automotive module supplier - Michigan



Need vendor for QPQ or salt bath nitriding in North America for large diameter parts

(2006)

RFQ: We are looking to locate a vendor who can complete a Salt Bath Nitriding (QPQ, Melonite, Tenifer, etc.) on some large cylindrical parts (the largest is 52" in diameter by 60" in length) In the past we used to hard chrome the parts but we rather do a QPQ process to ensure long life to the part
Thank you

Alan Guzowskiu
TechShop - San Jose, Costa Rica
^- Sorry, this RFQ is outdated
     View Current RFQs




Seeking melonite QPQ process in Far East (China, Taiwan, or Hong Kong)

(2006)

RFQ: Looking for QPQ / Melonite process for gears in China / Taiwan.

Andrew Olefson
Autoparts - Fort Lauderdale, Florida, USA
^- Sorry, this RFQ is outdated
     View Current RFQs




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July 28, 2008

Q. What does QPQ stand for?

don guidry
machine shop - Laf. Louisiana


July 31, 2008

A. Hi, Don. It stands for Quench-Polish-Quench. Please see the article for the details of what it involves.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



May 26, 2009

Q. We need to have full details of the Nitriding bath.

JAGMOHAN SINGH
- DEHRA DUN, Uttrakhand,India


May 26, 2009

A. Hi, Jagmohan. You would need to contact Kolene or Melonite for their technical data sheets and MSDS, depending on which brand you are interested in. These are proprietary processes and protected by patent and or trade secrets -- they'll give you enough information for your purposes, but they won't provide "full details". Do you want to know the properties of the deposit? Do you want to inquire whether you can license the process for installation in your factory? Are you looking for a licensed applicator?

If you can be a bit more detailed about your own situation, maybe we can refer you to some published info. Thanks.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



December 17, 2009

Q. I am looking into salt bath nitriding for some pivot pins. 100 ksi yield(1144/1045/1050). Looking for good corrosion resistance (250-300 NSS hours). Have been reading about the process but cannot figure out if nitriding messes with the temper or not. Also, do ASTM/SAE specs exist for this type of process? Seems that they are mostly proprietary. Any help is appreciated.

Thanks,

Brian Hoover
Product Designer - Greencastle, PA



March 14, 2013

Q. Is there any buildup on the parts from this process?

Dean Beenken
- Bethel, Minnesota USA



Permissible to shot blast nitrided surface to prep for blackening?

September 10, 2016

Q. Hello sir,
My client is having nitrided parts (with white nitride layer formed on top of the surface). Can we do shot/glass bead blasting to remove this layer?
We are facing great difficulty to do blacking on that surface. We tried cleaning with hydrochloric acid, but still the finishing is not acceptable.

Murthy RN
- Bangalore, karnataka, India


September 14, 2016

A. Plating on a nitrided surface is very difficult if not impossible.

If you blast deep enough to achieve easy plating, then you have probably destroyed much of the hard nitrided surface.

Best advise is to use the parts as is or use a different hardening process.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg,
      South Carolina




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